The only reason for attempting to repair a crack would be if the unit was an out of production color and nothing else came close to matching. And then I would only use an epoxy product to have the best chance of it not completely breaking. Even then I would be sure to advise the customer that there would be a good chance of a future flood.

: There is a crack in our toilet tank below the waterline. Previously it was patched with plumbers: putty; this has lasted about 7 years. Will RTV do: a better job, or is there something made for this: repair?